Communication system



July-16, 1946.l D. G. c. LUCK I 2,404,306

COMMUNICATION SYSTEM.

Filed April kJ., 1941 3 sheets-sheet 1 iy 36, i945. D, G, C, LUCK I 2,404,306

COMMUNICATION SYSTEM Filed April l,l 1941 3 Sheets-Sheel'. 2

fr @mm1-Geiz" L mame nventor July 16, 1946. D, G. LUCK COMMUNICATION SYSTEM 5 sheets-sheet s Filed April 1', 194i Patented July 16, v1946 COMMUNICATION SYSTEM David G. C. Luck, Haddon Heights, N. J assignor to Radio Corporation of America, a corporation of Delaware Application April 1, 1941, Serial No. 386,302

(Cl. Z50-G) 11 Claims. 1 vThis invention relates to communication systems, and more particularly to systems of the variable dot type, and has for its primary object to provide an improved variable dot signalling system.

Heretofore, dots of variable lengths and constant repetition frequency were produced from a signal wave by starting and stopping the dot at instants when the sum of the modulation signal and a triangular auxiliary Wave was zero. This resulted in a train of variable dots from which it was difficult to reconstruct accurately the original signal.

According to the` present invention, sequence switching of capacitance storage devices permit dot length to represent actual signal value at selected uniformly timed instants so that similar devices at the receiver may construct a rectilinear wave closely representative of the original signal. If it ispreferred, the dot length may be made to represent an average signal value over 4periodically recurring and successive selected periods.

Another object of this invention is to provide a variable dot signal more nearly a correct representation of an original signal.

Still another object of this invention is to provide a system to reconvert a variable dot signal into an original signal Wave more nearly a true representation of the original signal.

Other and incidental objects of the invention will be apparent to those 'skilled in the art from the following specification considered in connection with the accompanying drawings, in which,

Figure 1 is a circuit diagram showing one form of this invention in which signal waves are converted into modulated dots whose duration depends upon the instantaneous Value of the original signal waves at predetermined reoccurring instants,

Figure 2 is a circuit diagram showing one form of this invention for reconstructing an original signal wave from a Vmodulated dot signal,

Figure 3 is a graphical illustration of the derivation from a signal wave of the variable dot signal whose dot duration depends upon the instantanemodulated dot signal, in accordance With one f form of this invention, as illustrated by the circuit diagram in Figure 2,

Figure 5 is a graphical illustration of the cony.

version of signal trains to variable dot signals, in accordance with the prior art,

Figure 6 is also a graphical illustration of the reconstruction of a signal from the variable dot train, in accordance with the prior art, l

Figure '7 is a, circuit diagram showing another form of this invention for converting a signal wave into a dot signal, the length of the dots depending upon the average value of the signal during a predetermined recurring interval of time,

Figure 8 is a graphical illustration of the production of a variable dot train from ,a signal train, in accordance with the form of the invention shown by the circuit diagram in Fig. 7,

Figure 9 shows a circuit diagram of another form of this invention for reconverting modulated dots into a signal wave.

Figure 10 is a graphical illustration of the reproduction of a signal wave from a variable dot train, in accordance with the form of this invention as described in the circuit diagram of Fig. 9, and

Fig. 11 is a circuit diagram showing one form of this invention employing electronic switching means for converting a signal wave into a modulated dot train.

Fig. 5 shows curve a which results from superimposing an auxiliary saw-tooth wave train shown dotted as b having afrequency, for example, of 30,000 per second on a signal c such as, for example, a sine wave signal of 8000 cycles per second and having an amplitude f2 of the sawtooth wave amplitude,

It will be seen that, with such severe modulation, portions ofthe originally rectilinear auxiliary wave become distinctly curved. It is the information contained in this curvature that is lost in a variable dot type of transmission by the use of methods and means known to the prior art. The light and dark segments of the zero line indicate the yoff and on dot elements produced by limiting this wave to the neighborhood of zero, one well known method of producing modulated dots.

It is clear that reproduction from these dots 'which indicate nothing but crossing of the zero line by the composite wave can never be exact.

Fig. 6 shows a trainr of variable dots derived from the sine Wave in Fig. 5 by a method and means of the prior art such as briefly described above.

'I'his shows clearlythe small resemblance between the vvariable dot train .and the original signal.

Among the systems of the prior art, there is no generally accepted method of reconstructing the original signal from such a train of modulated represented by Fig. 5, and the original signal wave enhances the difficulty of keeping down the distortion of a reconstructed signal wave. Y

The transmission of relatively few Vdots, per

modulating cycle causes distortion Yand Vit lis therefore preferable that more dots per modulating cycle be transmitted. Since the use of Vsharp edged dots is obviously necessary to the noise suppressing function of theA systems, harn monies of the dot frequency must be transmitted, and-for dots or radio frequency energy each 'ofth'eseharinonics yieldsQal pair'` of sidefb'an'ds. Forretention oi a reasonable-^bfandjwidth, itis Iobviously 'necessary to reduce thenumber of dots transmitted per modulated Cyllasfaras possi- Thus 'for a givendegr'ee'of 'ni'se'suppr'es- "sion, Vthe dot repetition v'frequency chosen must bethe resultv of a'cornprornisebetween fidelity andband width.'v In'practice, the quality of reproduction obtained with only three or four dots per cycle of maximum vmodulation frequency is surprisingly good. Y

If only impulses marking the starting and stopping "instants of the dots are'to be transmitted, .the frequency band required.A ofcourse, Vbecomes very? much greaterf f By the use off sequence switches to charge'and kdischarge condensers, it ispossible 'to .control dot .duration'in accordance with'the 'magnitude of fth'efsig'nal at lthe'instant of stopping of the precedingdot.. Transmission of this type supplies 'information' about the actual modulation values at regularly timed selected instants. .-From this vdot signal, corrr'zlicate'd,l but realizable, switching arrangements permit a rectilinear wave having the'same values as the original modulation Vat the Lchosen dot cessation instants to be constructed.

. (Fig. 1 Visy a circuit'of a system employing mechanical switching means.. It is'well known that a `capa'cito'r'connected across a low resistance load e 'in.`a` Vacuum tube plate circuit will always, be :charged with a `voltage proportionallto the instantaneous value of the signal input tothe tube. Ii disconnected from the'tube and discharged vthrou'gh 'a constant current device, the time takento reach a iixed reference voltageis proportional to the value of the input signal at the instant of disconnection.

. A signal wave is applied to the input'circuit'of a low impedance vacuum tube I whose plate curre'nt is supplied' through a resistor 3. A synchronous Vmotor 5 drives the commutator including cap'acitors 'le 'and 1f. The speed of the synchro'- 'nous motor 5 will be Vdetermined by the repetition commutator revolves in a counterclockwise di'-V rection, as shown by the arrow, condenser" Ie vmoves to the discharge position and'discharges through a constant current device shown, for example, as a saturated diode 9. It will be noticed 'that `the lcondenser is inverted in its discharge VKposition such that the potential on the cathode and II. The voltage charge on the condenser 1e Y leaks ofi through the constant current device 9 such as tocause the control electrode of the gas tube I I to lgradually become less negative. When the potential on the control electrode of the gasY tube II reaches the igniting voltage, the tube II will ignite and pass current until the plate circuit of tube II is opened by commutator I3. During the interval in which the commutator I3 connects the segment I'I to the segment I5, such as to connect the gas tube I I in the circuit, a third commutator I3 connects the plateV I4 of the gas tube II to theY output circuit which contains a resistor I9 connected to a voltage source. While Athe tube VI I is conducting, the voltage across the output terminals'Zil will be small, bee cause of the voltage drop across the resistor I9.

Thus it will beseen that the output voltage will remain high for a period of time depending directly upon thevoltage charge of condenser 1e,

or an amount which varies in direct proportionV gas triodes I I and I2 rbecause of aY physical characteristic of a gas triode in which it isabsolutely necessary that lthe tube be completely extinguished before being reignited. In the case of high percentage modulation,Y the period allowed Vfor extinguishing the gas tube will be very small fand'in order to insurefproper operation, a pair of gas tubes is employed alternately. ,A single vacuum tube may be employedv in place of the gas tubes which makes it necessary to have only one "tube to perform this/step as it requires no time to lbe made non-conducting'.y

Figure 3 is a graphical illustration of the operation of the circuit shown in Fig. 1. For the purpose of illustration, a-sine wave is used and a dot repetition frequency equal to that illustrated in Figs. 5 and V6 is also used.' The dotted curve e rrepresents the potentialon the condenser 1e of Fig; 1. -It will be seen that during the interval of timetI, t2, condenser .'e is receiving a charge and at t2, when Vit is disconnected from the charging circuit, its charged potential is equal to the instantaneous potential of the incoming signal at the time r2.v Immediately upon'being disconnected, it is connected tothe discharging circuit through the constantl current device such that'its `potential decreases uniformly as shown by the uniformly sloping dotted curve e between t2 and t3. VAs previously explained, as this .time t3. Likewise, condenser 'If is allowed todischarge through vthe constant current device 49 such that a potential across the condenser'lf decreases from a highly negative potential to the predetermined reference voltage which ignites `the gas tube I2 such as to terminate a secondmodulated dot shown as the heavy line below the dashed linej in Fig. 3. The oif time of the modulated dot .determined by the charge on condenser 'If isV represented graphically .by the extension of Vthe `dashed curve f. and continues until time t4 when 'tube I2 is `disconnected and condenser 'If is returned-.to the repeated. .Y

- 1Fig.'2 showsV one form of this invention for reconverting modulated dots into an approximate vreplica of theoriginal signal wave. In the reconstruction process,.it is necessary to derive, from' the successive dot durations, voltagesfcorresponding Yto instantaneous valuesA of. the desired replica Wave at the instants of dot starting. and then to connect these instantaneous values into a continuous signal by rectilinearwave segments. `If va capacitor is connected across the output vconnected in series with a second constantcurf- Vcharging position, and the cycle is circuit-of a constant. current ldevice such as a.,

pentode amplifier tube it will be `charged with an amount of energy just proportional to the duration of the constant charging Signal.' A replica signal is thus produced from a modulated vdot vsignal and is representative of the original dot vmodulating signal. This may be accomplished by charging a capacitor with a constant current proportional to the length of one dot and simultaneously discharging it with a `constant current proportional to the length of the `preceding dot.

, Dot lengths may determine constant voltages, for

controlling the above mentioned constant currents, by controlling duration of Vconstant charging current intoan auxiliary capacitor.` kThe sequence of operations consists of four parts, each lasting for one dot and each requiring one auxiliary condenser. First, such an auxiliary capacitor is charged under dot control. Secondly, it is used to control charging current to an integrating capacitor. Third, it controls discharge currents kfrom the integrating capacitor and fourth, it is discharged prior to repeating the cycle.

This series of operations may be produced by the circuits shown in Fig. 2. An input signal of modulated dots is applied to the constant current device 2| with such a polarity'that the dot causes this device to pass current. AV synchrovnous motor 23 drives a commutator including condensers 25g, 25h, 252 and 257. For the purpose of simplifying the explanation, condenser 25g and its associated connection/'are drawn in heavy lines. In the position shown condenser 25g receives its charge during the dot portion of the interval during which the condenser 25g is connected in the output circuit of the constant cur- -rent device 2I. It will be noticed that there is no direct current connection between the source of potential and the anode of the tube 2| but it will be remembered that the storing of energy in condensers which are being periodically changed may supply anode current for the discharge device 2 I. It will thus -be seen that the series connection of condenser 25g in the plate circuit will cause it to have a charge whose voltage will be proportional to the duration of that dot portionof thetime 6 interval inwhich condenser 25g. is `connected' in the'plate circuit of the tube 2|.. This `positionvo'f the'condenser'25y is represented by. I...

As lallthe condensers, includingcondenser. 23g.,

moveto the second position such that'con'denser 25g,is` in position II the energy stored thereinis used toy control the charging current to theintee.;

grating capacitor 33-through a constant-current device 35/by causing its control electrode' 36 to be maintained at a potential which amount 'isr proportional to the amount of the vcharge received in the. position ,I of condenser 25g. This potential lremains substantially constant-during one com.- plete dotxinterval. n i It will `be 'noted that the discharge device 35 is rent device 31. During the complete, dot interval in which ycondenser 25g is in position 1I for maintaining` the control electrode 36 oftube 35 at-a constant potential depending upon "its 'previously receivedcharge condenser 257 has advanced to position III and its charge which was accumulated while it was in position Icausesthe control electrode 38 of tube V3'I to' be maintained at apotent'ialwhich is proportional tothe amount.` of

charge condenser 257' .received while in itslcharg-- ing positionl.` y

It will be seen that the resulting. potential across the integrating capacitor 33y is an amount which is controlled bythe current flowing through Y both tubes 35 and 3`I. It th'ereforef'ollows that theV potential across the vcondenser- 33 varies 1inearly between values proportional to thel instan.- taneous values of the original signal atsthe'instants of dot starting.

As the set of condensers including condenser 25g moves to their next position, such thatV con;V

denser 25g isvin position III, the charge oncon denser 25g controls the potential on the control electrode 38 of tube 31, while the condenser 25hl is controlling the potential on' the control elec-A trode 36` of the tube 35. During vthis intervalcon'- vdenser 251 is receiving its charge.

,In the Vfourth position, that is such thatco'n- Y Fig, 4 uiustrates graphicauy the operation` of the previously described -form of this, invention under Fig. 2. For the purpose of facilitating explanation the curves in Fig. 4 are given letters corresponding to the letters 'of' the` condensers in Fig. 2. The curves illustrate the potential on each condenser during the complete cycle. The input signal of modulated dots is represented by the heavy variable dots slightly below the zero axis. 1;

During the interval t2, t3, condenser 25g is in position I and receiving its charge throughl the constant current device 21 during thedot portion of the interval t2, t3. This is indicated by curve g which during the dot interval is increaseingly uniform until the time at which thesdot stops. yAfter the dot signal stops between t2, and t3, ,itwin ,be noticedthat the a. urregealeiaie a'uniiorm .amplitude untilltime `tilland.represents thevoltage `o'fcondense'r 2 5g.. It willibe seenth'at the chargeproduced ongthe condenserV ZSgTLdurin'g the no...signal rperiod, tl, .tzr .While .condenser s -257' Wasinposition .I is carriedoverto thetime in'- terval t3, V#L-During thetimeiinterval. t3, t4,

condenser 25g isV in positionv Ii 'asfshownin'the f 'accompanying chart .wherein'it 'is .controlling the potential on 'the control electrode '2.6 oftheltube 35. During `this same' interval `vlof time Y1:3, t4, [condenser 25'7 is .controlling the potential. on. the

control-electrode of the tube 31.' It, therefore, followsA that the potential across the integrating capacitor-33 Will change linearly-iromftheV potentialY representative of or. proportional to the y potential across the condenseri, whichisinturn 1 proportiona1 to the .value of the original signal Waveat instanttl, to that potentialrepresentative of .thepotentialjacross kcondenser Zgywhich is.proportional-tothe-value of the loriginal signal 1 at .instant t2.` This causesA the. outputY recon-` "egzioisoe' structed signal toctake the form ofV theheavy" curveofzlilig. 4.. l

sitionzlily is vthe snorting position- Therefore, .the

' dotted curved' will decrease rapidly lto zero las shoWninFigA.. :.liig. '1 shows a closely .relatedtype of converter using a somewhat simpler .variable dot-transmit` ter;V Instead of transmitting instantaneous .signal values'at instants beginningeach dot period and .joining these .values .by straight lines at the reconverter, itis possible to transmit kaverage Ysignal values over the dot period, and maintain,

.notimers.,thelponuallacrosscondenser 257' is shorted outibecauseas ,previouslydescribed po,-

the l:tube igniting voltage, current .flows through fthe.tube 51for the'remainder'of theldot period at which time the tube .51 is disconnectedfrom its source of anode voltagev which isfedto l.the commutator 58 -and through .resistor 5&5. This causes tube 51 to be..extinguished..V There results a variable dot Whose length is proportional to theiaverage value of the `signalwave duringfthe 'dot-period. Y

As .the condensers rotate to their. .next position suchthat condenser k is .in` position DI, `the remaining .chargeronfthe .condenser #57o is allovved .tofdischarge becauseof. being* short. cir.- cui'ted The cycle thenrepeats itselfs. 1

It vvvillbe noted that threev condensers are Y such that duringeach dot periodthere sone condenser on` charge anda diierent condenser Aon discharge, and .still another condenser'l Von short circuit, so that continuous operation iresults.

n There is also provided two additional gaseous discharge devices 6l and 63 which are connected to their respective segments 65 and 61 on the commutator such that each of the. gas discharge de.- vicesf51, 6I, and V63 operate only one-thirdof p the time and are soconnected to the commutathese value/s overeth'e dot periodlat the reconv vertente give a- :stepped rectangular approximation of the signal Wave.- On thegconverten averaging may .be accomplished by using a .constant current single tube plate currentto charge the capacitor; the cycle Vbecomes Y a a'three-part one, and `in addition` to the charge vand discharge of the capacitor, .a .position "for short circuiting or completely dischargingthe capacitor is also require'd'on'the sequence switch. y1

The receivercycleis also a three-'part cycle, using three capacitors cyclically-one on charge, one'supplying output signal voltage (no current),

' and one on discharge, short circ-uit.

According to the form of this invention shown in Fig. '7, there isshown one form of this inventio'n in which the average amplitude of the incoming amplitude modulated signal is used to charge a condenser to Ybe later discharged. A

.signal Wave is applied .to the constant current disi charge 'device 39. Asynchronous motor I3 drives a commutator includingcapacitors 451 c,'45vl.and

' tor'thaty they operate sequentially.

115m., "l/' hile condenser'lllcis inposition I, it is receiving a. charge which is proportional' to the time integral of `thevvoltage 1 impressed upon Athe discharge device vit by the vsignal Wave during 'the corresponding dot period. yThischarge vresults from the series connection of the condenser 45k Vfrom the voltage source supplying the ya'ni'od'e c-urrentoof tube "39. V'.Ait'the end of this-dotperiod,

. the accumulated charge on condenser lilik i'spro- YWave,during the'period.

portional to the time average of the signaling As the condensers ro'tateisothatv condenser 'Mik is imposition II, itis discharged'through a conetant current device which takes theform of -a saturateclfdiode-5i'.-V Y' yf `secondco'mniuta-tor also driven by-thelsym chronous moto-r '43 includeslacommonsegment `tasconnectedto the-cathode@ theconstant cur- Fig. 8 shows graphically the operation ofthe .form of this inventionas set forth in Fig. 7., The letters representative of the storage condensers in Fig. lT are used in each of the curves in Fig. 8. to facilitate th'eexplanation ofthe operation, and :the Ycurves in Fig. 7 are rrepresentative of the potentials `across the storage l condensers., The ,dashed line k represents the voltage of the con- ,denser 45k, the dottedline l represents th'e volt- `age on the/condenser 451,.and the A dash-clot line m represents the voltage on the condenser vllm'. `A sine wave is used.- and is divided up'into dot inter; vals similar to those vused in yprevious Avvexplanations of other forms of'this invention,

During the interval tlLtZ, the condenser 45k is in .position I and is assuming a charge Vwhich is proportional tothe average amplitude'ofthe'incoming amplitude modulated signal during'the "time interval tl, t2. At time t2, the commutator has rotated such as' toy place condenser 457C in position IIat which 'time it starts to discharge Vthrough thev 'constant current device 5 l'. This ac"- counts for |the uniform decline taken by curve k v:starting at it?. Al/"Ihenthe potential on the con- "denserjfdecreasesto the potential at which the lgastuloe will ignite, a cessation of the variable 'dot' occurs, the length of the variable dot,r as previvously described, continuing from the instant1t2 until the ignition of the tube 51. The condenser continues along the base line between time interval t3 and tf1 during which time condenser 451C is'inrposition IILzor discharge position. At .time

t4, condenser 55k is again in the charging position, lor position I and assumes its charge at a, ratepro- `.portional to the area under th'e signal Wave or to van amount which at t5 .is in turn proportional to the average amplitude of the signal Wave .during vperiod t4 to t5.

At. the beginning `of theldot 'the output circuit.v

charge.

yItwill loe-seen that each' of the condensers op; erate in a similar manner `and sequentially such that they producethe desired variable dot signal.

Fig. 9 shows a reconverter circuit to reconvert the variable dot train into a replica of a signal wave whose averagel amplitude during one dot period is proportionalto the dot length. The modulated dot train is applied tothe control electrode 64 of a constant current discharge device 65.y The output circuit also includes a commutator driven by a synchronous motor4 |59. The commutator includes capacitors 1Ip, 1|q and 1|r. As the condenserg are in such a position that condenser 1|p is in position I, the condenser 1|p is receiving a charge whose stored energy will be proportional to the signal portion of a dot interval. I

As the condensers rotate such that condenser 1| p is in position II, the condenser 1 p will maintain across the output a' voltage corresponding to the charge which it has accumulated; The output signal will therefore have a magnitude proportional to the length of the dot which lcharged the condenser 1 I p when it was inthe iirst position I.A l I f As the condensers further rotate such that "condenser 1| p is in positionv III, the condenser 1 p is short circuited such that the remaining energy therein is discharged. Therefore, when it g return's'to the chargin'giposition, the'voltage produced across it is directly proportional Vtothe charge'whichl it accumulates.

and a third'conden'seris in the position of short 4circuit preparing itself for. its next charge.

The resulting signaiwave is appned tothe conftrol electrode 12 of the outputV tube 14. It `will be notedthat tiere isn'og'rid ieakfresister. This Venables the condensers to'A holdV their charge throughout the/timeintervalas shown in Fig. 10.

Fig. is a graphicalillulstration of the operation of the form of this invention shown in Fig'. 9. DuringV the'dot portion of interval tl, t2 condenser 1|p is'receiving its 4charge lthrough the constant kcurrent device 65. This may be seen from the uniform slope of the dotted curve p. When the variable dot signalvceases during the time intervall t|t2 ,thev tube 65 is biased beyond cut-'olf so that the condenser 1|p reecives no further charge due to the Afact that no` current is flowing in the outputcircuit of the tube 65. It will be seen that during the no signalI portion of time tl t2, the dotted curve "p maintains its arnplitude and at time t2 when the condenser 1|p is changed "to position I'I, the voltage across the condenser 1,|"p is connected across the output circuit, and for the period 't2, t8 the output signal iseequal to the voltage on the condenser 1 p.,

At time t2 condenser *1|'r is connected to the charging circuit so that potential across 1|r increases as represented by dash-dot line r during the signal interval of time t2, t3. A'Upon cessation of the rvariable dot signal, the tube 85.again is bleck'ed causing the condenser 1|r to maintain its voltage through the remainder-'of the dot interval t2, t3, andv throughfthe interval t3. tellV during which time theV condenser 1 Ir is connected in Attime r3, the third condenser mi` does on The potential of the'condensers 1| qisV 'shown asl dashed line lq. As each of the Vcon- -densers reachLp'osition. III, they are discharged .1() anddrop in potential immediately to the axis where they remain until they again assume posi# tion I-to take on acharge for the vnext'succe'eding cyclej ofA operation.` It `will be readily seen that by repeating'this cycle of operation, a complete reconstructed signal wave will be' produced. Fig'. 1l shows one form of this invention' in which electronic meansis used for switching rather than the mechanicall means previously shown and described. A i I g It will be noticed that two similar channels'are provided for theconversion of a signal waveinto a modulated"dotsignal and each channel'works alternately. ,i i 'j l l A squarewave generator 11 ofV any of the well'- kriowntypes produces av push-pull; square Vwave signal,A such thatfits output voltage will vary sud,-r

f denly between apredeterrnined positive potential and aV predetermined negative potential. *n

A signal'wave input is applied'simultaneously to the control electrodes 19and 8i) of' the dis- Y charge devices' 8| andf82; Simultaneously the output signal from thesquare'wave generatoris appliedfto anauxiliary electrode 83 Yof the disi charge device 8| in a positive directionsuch'that it causes the discharge device 8| to 'pass current During the same interval that the positive poten.- tial is being applied to th auxiliary electrode 83, a negative potentialis applied'to the auxiliary electrode' 84 ofthe discharge"device 82 such'that the currentflowing through'th'e discharge device 82 will be blocked. During this interval, a" storage condenser 85 is receiving a vclriaJrge which is pro- `portionalto the* magnitude of theinput signal by reason of the Yvoltagejdrop vthrough resistance ysi and diseh'argecevice 'as` which has vbeen made conducting during the vtime the discharge device v8| isdrawing current, f i Y During `the next succeeding dot interval, the

constant current y deviceA 9| Y is made conducting vby reason'of its auxiliary electrode 93 being connectedto the output signal ,from4 the square wave generator, whichis at a positive potential Vduring the interval;v

The charge which has accumulated on vcondenser is prevented from leaking off through resistor-81 'and` tube 89 by reasony of theV tube 8S being made nonconductive during the interval thatv th'ef'constant current device 9| is made conducting.' During this interval that constantcurrent device 9| is made conducting the charging tube 8| is made non-'conducting by the negative wave vapplied to its auxiliaryelectrode 83 by'- the square wave generator 11.

By reason of the fact that the constant current device9| allows theA charge on the condenser 85 toA leak off therefrom at a uniform rate, the potential at thecontrol electrode decreases uniformly. It follows, in View of the phase reversing action of the discharge device 91., that the potential on the control electrode 99 of the gaseous discharge device IUI, which is in a nonvconducting state, increases in a positive` direction during this uniform decrease of potential on the control electrode: 95, of tube 91. When the potential on the control electrode 99 reaches a predetermined value, thetube ||l| will become concharge which-thecondenser 85 originally received byreason 'of thev magnitude of the inputsignal at the instant when. the l condenser 85 was re- -moved fromwthe charging circuit and-placed on afrogsoc Y ther discharging circuit Vby reason of Vthe control voltage from the square wave generator; 'Y 'Y During that time which the tubelil is conducting,V the potential on the control electrode 'i |03 Vof the4 tube,V |05 .is low; resulting in-anaccompanying high voltageon the anode-lluof the tube-|ll5-Y This results inl a .modulated dot ksignal 1 whose durationis dependent upon, the time :which thetube lill is conducting; Y

Because of the fact thatthe'gaseous discharge l device must be extinguished, an auxiliary gaseous discharge device. IBSY-is provided 'whosecontrol 1 .electrode H I'is also connected to thesquare Wave l generatori" such that the control electrode HI will gopositive toV make the tube Ill-9 conducting at jthe end of'the interval .during which tubel0! lis conducting. The instantaneous pulse resulting from the-tube-lllllY becoming conductive-'is vimf pressed upon the output Acircuit of tube lill 1 through a--coupling condenserL Irlv'such that it produceslafsuiiicient voltage dropY in the output 2 circuit oftube ill-Ito cause -it to be extinguished i -byreason of the fact that, when'the anodesupply i V voltage-of a 'gaseous discharge -device drops below a predetermined amount, the gaseous rdischarge Y .Y

device is extinguished. Y

,Y VIt will'be seen that, at eachV succeeding dot nate dotsrof the Vmodi-il-ated'dotsig-nals are producedby alternate-use offthe channels shown. n The Aoperxgal-tion of the `second channelais precisely the, same as theA operationfcf the rst channel. Y Itwill be seen that this will producea train of :modulated dots, the durationof'eachdot of which is representative ofthe :magnitude 'of the input 4 sig-nalaat one of aset of predetermined,y periodii -callyrecurringinstants.`

interval, the channel is changed such -that alter@- Ythe resulting'potential across said constant kcurrent device. Y n

4. In a, signaling system; means for converting a -periodically reoccurring variable dot train into a signal wave wherein themagnitude thereof is representative of the duration of the variable-dots comprising in Ycombination means 4for sequentially changing the charge in -eachA of; a plurality ci condensers at said ratev and by an amount-deter-VV mined Aby theV duration of said-,variable dots, a pair of constant current devices havinginput circuits and serially connected output circuits,

means for sequentially connecting said'condensers toY eachof said input circuits in apredeterf mined order and duringjeachgof the time intervals occupied by avariable dot; -l Y f 5. In a signaling system, .means for converting Y a signal wave into a trainfof' variable dots -greoc'- curring at a predetermined rate and wherein ,the

duration of the dots is representative of the magnitude of said signal wave-comprising in'V combination meansfor sequentially chargingxeachwof While several systems forcarrying thissinvenf it will'rbe apparent'to oneskilled in the art that ticular organizations Yshown and described,` but l thatgmany modications may be made without Ydeparting from the scope of this invention asset forth in the appended claims.

IA. claim as. myl invention: f 1 In a :signaling system, means for a signal wave into a' train nf variable,dotsrenc' magnitude-of AVsaid signal wave comprising in combination,A means for sequentially charging each of` a plurality of condensers a-t'saad rate .andby an amount determined by the magnitudeofzsaid Y signaling wave, means for sequentially connecting; eachV of said condensers to a constant .cur-

rent discharge device at `said predeterminedrate, g

and av discharge device connected .to said con` stant current;A device whose conduction is controlled by the resulting potential across said constant current device. Y i 2.' In a signaling system, means for' converting a'periodically reoccurring variable dot train into a signal wave wherein the magnitudethere- Vofis representative of thesduration-of the variable .dots comprising in conrbinatien,Y means for se*- .quentially changing the chargein each of` a pluv ,ralityof condensers atsaidateandby anamount determined :by the durationof said variable dots, va :signalftransmission circuit Vandvrrneans for se- Y i'.luentially connectngsaid: condensers to said;

transmissioncircuit for controlling the` produc- ,tionY of a signal wave'in` said .transmission circ'zuit@V 3 ,g ^3.,In-asignaling. system, .means for converting j a signal'wave into a .trainyof variabledots .re-

'ccnverting f tion into eiect have been indica-ted and described,

this invention is by no means limited to the 'par- 140 a plurality'of condensersatsaidrate and v*by an amount determined'byy the magnitude Vof said` signaling wave, means for 'sequentiallyconnecting each of said condenser's to a constant current discharge device at said predeterminedrate,y and means for controlling the period, and means yfor controlling the period ofaconduction ineachoi a plurality "of gaseous discharge devicesl during predeterminedintervals reoccurrlng-at said peri odic .rate with the resulting lpl'ltential :across 'said constant current device during said interval.Y

6. In a'signaling system,V means :for converting Y a'signal wave-into a train of variable dotarel `currin-gat a predeterminedrate and vwherein the Y duration ofthe dots is representative of the ,50

j the steps Yof -sequentiallygderiving individual electric charges' proportional to the magnitudefofaf Y.signaling jwave, .allowing .the energy. in` eachgoi occurring at Y aw-predetermined 'ra-teand wherein the duration of the dots is representative ofthe magnitude of saidV signal wave comprising gin com"- -binationV a pair -of signal channels, means for alternately applying'toeach of said channels alternate dots of said variable dottrain, each channel includingna condenser, meansfor applyingtosaid condenser a charge representative Aof the magnitude-of said signal wave in the respective dot interval; a constant current .deviceA connected'V to said condenser, means forapplying the potential across said constant current device to the input circuit of one o1 a pair of gaseous discharge devices whose output circuits are connected in par-V allel fo;i controlling theignition thereof, ymeansV connected to the input circuit of the other of said gaseous discharge devices for ignitingthe other of said gaseous discharge devices at the beginning of therespective dot intervalto'uextinguish the Y iirst of said gaseous discharge devices, andY a variable dot transmissionchannel connected to Vboth of said signal channels for .transmittingthe resulting train of variable dots. 1 Y,

7. VThe method of signaling which comprises the charges to'be dissipatedfat. a constant; =rate 13 v and utilizing the charge to control the ow of current in each of a plurality of discharge devices sequentially to produce a train of periodically reoccurring dots Whose duration is proportional lto the magnitude of the said signal Wave.

8. The method of signaling which comprises the stepsy of sequentially deriving individual electric charges proportional to the duration of the variable dots of a variable dot train and sequentially utilizing the charges to produce a signal Wave whose magnitude is proportional to the duration of the variable dot train.

9. The method of signaling which comprises the steps of sequentially deriving individual electric charges proportional to the magnitude of a signaling Wave, allowing the energy to be dissi- -V pated at a constant rate and utilizing said charge charge dissipation for producing electrical pulses varying as the periods of said charge dissipation, Wave signaling receiving apparatus including means for sequentially producing another plurality of electrical charges at said rate and of a magnitude determined by the duration of said pulses, and means sequentially `responsive to said other electrical charges for reconstructing said signaling Wave.

11, The combination of a Wave signaling transmitting apparatus including means for Vsequentially charging one plurality of condensers at a predetermined rate and by an amount determined by the magnitude of the signaling Wave, means for sequentially connecting each of said condensers to a constant current discharge device at said predetermined rate, a discharge device responsive to the potential of said constant current device for producing electrical pulses varying as the potential of saidconstant current device, a wave signaling receiving apparatus including means for sequentially changing the charge in each of another plurality of condensers at said rate and by an amount determined by the duraf tion of said pulses, andmeans sequentially responsive to the charges of said other electrical condensers for reconstructing said signaling Wave.

DAVID G. C. LUCK. 

